(;
AB[ns][nr][nq][op][pp][qp][rp][qs]
AW[sr][rr][rs][qq][oq][or][os]
C[Black plays.]
(;
B[pq]
C[Bad timing.];
W[pr];B[qr];W[ps];B[qr];W[rq];B[qs];W[pr]
C[White's under-the-stones play here saves the corner.]
)
    (;
    B[rq]
    C[Too slow.];
    W[qr]
    C[White easily makes a 2nd eye.]
    )
    (;
    B[qr]
    C[The only move.]
    (;
    W[pr];B[rq]
    C[Black must atari from this side!];
    W[ps];B[qr]
    C[Now White does not have any under-the-stones saving move.];
    W[qs];B[pq]
    )
        (;
        W[pq]
        C[An interesting defense, but ...];
        B[rq]
        LB[sq:A]
        C[... after Black cuts here, the seki to the left is only temporary.  Black only needs to play at A to capture the corner stones.]
        )
    )
)

